cDNA probes of human glutathione peroxidase (GSHPx) genes, including the classic GPX1 (GSHPx-1), the newly characterized GPX2 (GSHPx-GI), the plasma enzyme GPX3 (GSHPx-P), and the phospholipid hydroperoxide glutathione peroxidase GPX4 (PHGPX), were hybridized to Southern blots containing genomic DNA from human x hamster somatic cell hybrids. GPX2 was mapped to chromosome 14, GPX3 to chromosome 5 and GPX4 to chromosome 19. Additionally, human chromosomes 3 and 21 and the X chromosome were shown to contain sequences homologous to GPX1, as reported previously.